The present invention relates generally to on-board vehicle computer systems and, more particularly, to a service adapter for allowing access by existing diagnostic tools to new on-board vehicle computer systems.
For over a decade, computers have been used on vehicles to control various vehicle systems such as engine and transmission systems, brake systems, suspension systems and even motorized seats. Due to the complexity and inter-relationship between some of these vehicle systems, on-board computer communication systems have been developed to enable data and control signals to be passed between particular vehicle computers. These communication systems typically include a plurality of wires which are connected to the vehicle computers in a particular electronic configuration, generally referred to as a "bus".
One example of vehicle bus structure is represented by the Chrysler Collision Detection ("C.sup.2 D") Serial Data Bus. This technology is described in the following publications and patents: SAE paper No. 860389, entitled "Chrysler Collision Detection (C.sup.2 D)--A Revolutionary Vehicle Network", by Frederick O. R. Miesterfeld, 1986; SAE paper No. 890529, entitled "The All-Adaptive Controls for the Chrysler Ultradrive Transaxle", 1989; U.S. Pat. No. 4,706,082, entitled "Serial Data Bus For Intermodule Data Communications," which issued on Nov. 10, 1987; and U.S. Pat. No. 4,719,458, entitled "Method of Data Arbitration and Collision Detection In A Data Bus," which issued on Jan. 12, 1988; and U.S. Pat. No. 4,739,323, entitled "Serial Data Bus For Serial Communication Interface (SCI), Serial Peripheral Interface (SPI) and Buffered SPI Modes of Operation," which issued on Apr. 19, 1988; and U.S. Pat. No. 4,739,324, entitled "Method for Serial Peripheral Interface (SPI) in a Serial Data Bus," which issued on Apr. 19, 1988; and U.S. Pat. No. 4,742,349 entitled "Method for Buffered Serial Peripheral Interface (SPI) in a Serial Data Bus", which issued on May 3, 1988. These co-assigned patents and the identified publications are all hereby incorporated by reference.
In order to permit the bus itself to be tested and to permit direct access to and communication with any of the vehicle computers tied to the vehicle bus, the serial data bus may be accessible to an off-board vehicle computer, such as an attachable diagnostic tool. One such tool is the DRBII Diagnostic Readout Box that is commercially available to Chrysler dealerships. Another is the more advanced DRBIII diagnostic tool described in U.S. patent application Ser. No. 08/083,050, filed Jun. 25, 1993, entitled "Automotive Diagnostic Scan Tool". This co-assigned application for patent is also incorporated herein by reference. This type of diagnostic tool is typically employed to conduct serial communications directly with the on-board vehicle computers during certain diagnostic procedures. Thus, for example, data being gathered by the on-board vehicle computer from various sensors (such as engine speed and manifold pressure) may be transmitted to an off-board computer for programmed or operator directed analysis.
Such a diagnostic tool may also be used to enable a test program from an off-board computer to be "down-loaded" into a vehicle-based computer system in order to execute one or more prescribed tests of various vehicle systems before the vehicle leaves the manufacturing facility. The nonvolatile memory of one or more on-board vehicle computers can even be reprogrammed at a later date through a communication link between an off-board controller and the signal transfer structure of the vehicle via an appropriate diagnostic tool. This reprogramming process is described in greater detail in a co-assigned patent entitled "System and Method for Reprogramming a Vehicle Computer", issued on Jan. 11, 1994 as U.S. Pat. No. 5,278,759, the contents of which are also incorporated herein by reference.
In response to the heavy reliance on such on-board computers, combined with a variety of systems employed by the various automobile manufacturers, future vehicles sold in the United States will soon be required to provide a standardized diagnostic interface to facilitate compatibility with standardized diagnostic scan tools. This restriction is referred to as the CARB/OBDII (California Air Research Board/On Board Diagnostics II) requirement and applies to new vehicles beginning in the 1994 model year and all vehicles in the 1996 model year. The CARB/OBDII requirement offers a choice between several communication protocol specifications, among them ISO9141. The OBDII requirement and the ISO9141 are hereby incorporated by reference.
The on-board computer systems in new vehicles will necessarily be in compliance with the CARB/OBDII requirement and therefore able to use ISO9141 standard communication to supply information to general industry scan tools, such as for example, those used to perform emissions tests. However, communication solely under the ISO9141 standard will thereby render existing diagnostic tools such as the DRBII, which operate using SCI standard signals, incompatible with the new vehicle on-board computer systems. There is therefore a need for a means to interface existing diagnostic tools such as the DRBII with the new vehicle on-board computer systems which are in conformance with the new CARB/OBDII requirements.